The incomplete return of function following peripheral nerve injury has long been a challenge to both basic and applied neuroscientists interested in the plasticity and specificity of nerve regeneration. Despite recent advances in microsurgical repair, many fundamental questions remain obsecure. Among those factors which influence nerve regeneration, is the role of an electric field produced by applied ionic and electrical currents. In vitro studies have shown that neuron processes grow preferentially toward the negative electrode, but in vivo experiments on mammalian nerves are lacking. Therefore, we will study by quantitative light and electron microscopic methods the effects of electrical stimulation on nerve regeneration. Implanted wick stimulators will deliver minute D.C. currents to the nerve segment distal to crush, transection and gap lesions of the rat peroneal nerve. Variables of the electrical stimulus and the effect of prior conditioning by crush lesions will be examined. Following survival times of two weeks, one month and six months, the distal nerve morphometry will be measured for the nerve fiber number, diameter and density, as compared to control values by statistical analysis. The return of the toe-spreading reflex will indicate the recovery rate of motor function. Other methods will be used to determine the effects on sensory vs. motor fibers, neuromuscular junctions, muscle fiber hisotchemistry and retrograde response in neuron cell bodies. These results will have application to improvement in human nerve injuries and to future success in mammalian regeneration in the central nervous system.